1. Field of the Invention
The invention relates to a fuel tank for storing fuel and, in particular, to a fuel tank for an engine.
2. Description of the Related Art
Fuel vapor may be generated if a space is formed above a fuel surface in a fuel tank. Generally, an interior of the fuel tank is in communication with the atmosphere in order to discharge the air above the fuel surface which rises when the fuel is refilled in order to aid the introduction of the fuel into the fuel tank. Thus, the fuel vapor may be discharged from the fuel tank to the atmosphere when the air is discharged from the fuel tank. In the fuel tank disclosed in Japanese Unexamined Patent Publication No. 8-170568, a fuel tank has a fuel chamber which has an interior volume which changes according to the change of the amount of the fuel therein. In this case, the interior volume of the fuel chamber changes according to the change of the amount of the fuel therein so that no space is formed above the fuel surface in the fuel chamber. Therefore, the generation of the fuel vapor is prevented, and it is not necessary to discharge the air above the fuel surface when the fuel is refilled.
The fuel chamber of the fuel tank disclosed in the above publication No. 8-170568 is defined by a sheet which has a bellows portion. The interior volume of the fuel chamber is changed by the stretching or shrinking of the bellows portion of the sheet. When the fuel moves in the fuel chamber, the moving fuel bumps into the bellows portion and the bellows portion is locally extruded. Thus, a load is concentrated on a part of the bellows portion, and then the sheet may be deteriorated or damaged. As described above, the fuel tank may be deteriorated or damaged by a various causes. Therefore, the object of the invention is to provide a fuel tank which can prevent the generation of the fuel vapor and has a high durability.
According to the invention, a fuel tank for storing a fuel therein is provided, comprising a pair of spaced deformable thin walls and a deformable side wall extending between peripheral edges of the thin walls, the side wall and the thin walls defining a fuel chamber therein, the thin walls and the side wall being connected with each other to cause the side wall to expand inwardly when the thin walls expand outwardly.
Further, when an amount of the fuel in the fuel chamber exceeds a predetermined amount, the thin walls expand outwardly.
Further, when the amount of the fuel in the fuel chamber becomes lower than the predetermined amount, the thin walls expand inwardly, and the side wall expands inwardly due to the expansion of the thin walls.
Further, the thin walls have polygonal shapes, respectively.
Further, the shape of the fuel tank is parallelopiped.
Further, the thin walls have four side edges, respectively, and the side wall has four side sections connected to the side edges, respectively.
Further, corners of two of the side sections together with corners of one of the thin walls form a point.
Further, the side sections expand inwardly simultaneously.
Further, the side sections have rectangular shapes, respectively.
Further, means is provided for stopping the expansion of the thin walls when the thin walls expand outwardly beyond a predetermined extent.
Further, means is provided for preventing the expansion of the side wall when the side wall expands inwardly beyond a predetermined extent.
As recited in claim 3, the connecting wall contracts inwardly not only when the amount of fuel in the fuel tank exceeds the predetermined amount, but also when the amount of fuel in the fuel tank becomes less than the predetermined amount. That is, as the distance between opposite edges of the thin wall decreases both when the thin wall expands outwardly and when the thin wall contracts inwardly, both expansion and contraction of the thin wall pull the edges of the connecting wall inward.
Further, the expansion preventing means comprises projections extending outwardly from the side wall and the projections abut against each other when the side wall expands inwardly beyond the predetermined extent.
Further, one of the thin walls is located above the other thin wall, the lower thin wall has an opening for introducing the fuel into the fuel chamber, and means is provided for introducing the fuel through the opening in a direction along a plane including the lower thin wall.
Further, one of the thin walls is located above the other thin wall, a pipe for introducing the fuel into the fuel chamber is connected to the lower thin wall to form an angle smaller than the right angle between an axis of said pipe and a plane including the lower thin wall.
Further, one of the thin walls is located above the other thin wall, and the lower thin wall has an oval opening for introducing the fuel into the fuel chamber.
Further, one of the thin walls is located above the other thin wall, and the lower thin wall has a plurality of oval openings for introducing the fuel into the fuel chamber.
Further, the rigidity of the side wall is larger than that of the thin walls.
The present invention may be more fully understood from the description of the preferred embodiments of the invention set forth below, together with the accompanying drawings.